Encapsulant films used in PV modules have several requirements, including good adhesion to various components, the ability to protect the PV module and solar cells and prevent moisture penetration to the cells, and good electrical insulation. In addition, encapsulant films must permit maximum light passage to the solar cells to maximize power generation.
All cell materials have some limitations when it comes to the wavelengths the materials can effectively convert to electricity. For example, some portions in the UV region and IR region cannot be effectively converted into electrical power. This is wasted energy.
In order to capture this wasted energy, materials which up-convert or down-convert otherwise unusable wavelengths to usable wavelengths are desired. For example, down-converting materials take UV-wavelength photons and convert them to longer wavelengths that can be used by the solar cells. Similarly, up-converting materials take IR-region photons and covert them to shorter wavelengths that can be used by the solar cells. These converting materials, however, have efficiency and cost limitations. Such up-converting and down-converting materials typically have lower optical transmission in the useful spectrum or require such a large amount of additives that it is not cost-effective to implement the films.
A need exists for low cost encapsulant films that down-convert unused UV wavelengths to lower energy photons which could be absorbed by a PV cell to increase cell efficiency and reduce module temperature.